Polyculture and integrated aquaculture are methods of raising diverse organisms within the same farming system, where each species utilizes a distinct niche and distinct resources within the farming complex (Figure 2).
This may involve the rearing of several aquatic organisms together or it could involve raising aquatic organisms in conjunction with terrestrial plants and/or animals.
In either case, the wastes from one organism are used as inputs to another, resulting in the optimal use of resources and less pollution overall.
Polyculture systems can provide mutual benefits to the organisms reared by creating symbiotic relationships while allowing for a balanced use of the available aquatic resources, whereas intensive monoculture systems extract resources from the system and place more stress on the surrounding environment.
In addition, integrated systems can increase the economic efficiency of fish farms through improved conversion rates of input materials.
Polyculture and integrated:
aquaculture have the potential to address some of the problems that arise from the intensive rearing of single finfish species. For example, the integration of fish culture with the culture of algal and/or shellfish species shows potential for reducing the risks of eutrophication and also for exploitation of the large amounts of wastes produced by fish farms. Further research is needed however, to determine the effectiveness of such systems, especially in open marine environments.
Polyculture systems are not a new concept; on the contrary, they have been used for centuries. For over one thousand years fish farmers in China have produced four of the most widely cultivated fish species together in the same pond: silver carp (a phytoplankton filter feeder), grass carp (a herbivorous plant feeder), common carp (an omnivorous feeder), and bighead carp (a zooplankton filter feeder).
This type of system utilizes available food and water resources, with the effect of reducing costs and increasing efficiency and production. Although still experimental, other systems, such as the integration of seaweed, fish, and abalone culture, and the polyculture of shrimp and tilapia, have proved to be ecologically efficient methods for growing a variety of organisms and may increase profits at fish farms.
It should also be noted that although polyculture systems based on netpens may prove beneficial for waste reduction, they fail to eliminate other problems associated with netpen aquaculture, specifically escape of fish, disease transfer, and discharge of chemicals.
Kathryn White, Brendan O’Neill, and Zdravka Tzankova